Essentially what they found was that during the surveillance period between 2007 and 2008 H3N2 influenza viruses were regularly detected from domestic pigs in Jilin Province, China.

Phylogenetic analysis showed two distinct lineages:

One that closely matched the contemporary strain of human-like H3N2 viruses

And another consisting of double-reassortant viruses containing genes from human H3N2 viruses and avian H5 viruses.

It’s a long and informative study (with a lot of technical detail on how it was conducted), but their conclusion reads:

Conclusions

The present study reports for the first time the coexistence of wholly human-like H3N2 viruses and double-reassortant viruses that have emerged in pigs in Jilin, China. It provides updated information on the role of pigs in interspecies transmission and genetic reassortment of influenza viruses.

As we’ve talked about many times before, pigs have long been believed to be ideal `mixing vessels’ for influenza because they possess both avian-like (SAα2,3Gal) and human-like (SAα2,6Gal) receptor cells in their respiratory tract.

That means pigs are susceptible to human, swine, and avian strains of flu. And they are capable of being infected by more than one flu virus at a time.

This raises the possibility that two flu viruses could swap genetic material inside a pig, and create a hybrid (reassortant) strain. One that could go on to infect humans.

This is basically how the 2009 H1N1 pandemic virus evolved, although it took multiple gene swaps over a decade or longer before it finally emerged into the human population.

We know that reassortments happen, but only rarely do they result in a biologically fit virus capable of causing a pandemic. Most hybrids are evolutionary dead-ends and die out within the host.

But as global pig production grows to meet the demands of a hungry world we have a rapidly escalating global pig population - playing host to numerous strains of human, swine and avian influenzas – all of which creates increasing opportunities for a new virus to emerge.

Crowded factory farming techniques, the transport of live pigs across long distances, and a lack of biosecurity controls and surveillance at many pig farms around the globe all compound the risk.